This invention relates to a method of producing a liquid-crystal display device in which active elements thereof are arranged in a matrix form.
In accordance with a conventional method of producing a liquid-crystal display device using thin film transistors as active elements, the display device is produced after passing through seven masking steps, as depicted in FIGS. 1a to 1g. First of all, a gate electrode 1 is formed on a substrate using a first mask (FIG. 1a), and a picture element 2 consisting of a transparent conductive film 2 is then patterned using a second mask (FIG. 1b). A gate insulator film 3 is formed over the gate electrode 1 using a third mask (FIG. 1c), and a thin semiconductor film 4 is then formed using a fourth mask so as to cover at least past of the gate electrode 1 and the gate insulator film 3 (FIG. 1d). Source and drain electrodes 5 and 6 are simultaneously patterned using a fifth mask (FIG. 1e), and then an insulator film 7 is patterned over the source and drain electrodes 5 and 6 using a sixth mask so as to open at least an electrode lead-out port (FIG. 1f). Finally, a light-shielding film 8 is patterned using a seventh mask (FIG. 1g). Since the number of masking steps is so large, the production yield is inevitably lowered.